1. Field of the Invention
The disclosure relates generally to an apparatus for improving server electromagnetic shielding, and more particularly to an apparatus for improving server electromagnetic shielding at high and low frequencies.
2. Description of the Background
Typically, a casing of a server will include a relative back surface (or portion thereof) that includes or defines a plurality of openings for allowing air to flow out of the server. Along with effecting airflow from the server, the characteristics of this surface affect electromagnetic compatibility (EMC) of the server with other electronic equipment in the server's environment. EMC is the measure of unintentional generation, propagation and reception of electromagnetic energy, and the unwanted effects that such an energy may induce in an electronic component environment. Depending upon surface composition, the relative back surface will have different levels of effectiveness in shielding the server from various electromagnetic frequencies. For example, if the surface comprises conductive fiber filled plastic that is molded into a plurality of bosses (i.e. opening structures extend into the server), it will effectively shield the server from high frequency electromagnetic energy. This is because the penetration of the bosses into the server results in an increase of the effective thickness of the opening pattern. With the bosses acting as waveguides that penetrate into the server beyond its junction with the back surface, shielding effectiveness of the structure, at any frequency, is improved.
However, the essentially internal conductive fibers will be less apt to conduct lower frequency energy, rendering the plastic surface less effective at lower frequencies. This is because the conductive fiber filled plastic is manufactured to include a thin skin of non-conductive resin. This resin makes it difficult for low frequency current to contact the internal fibers. Low frequency energy that cannot contact the conductive fibers, and thus be allowed to smoothly transition through the plastic back surface, creates a radiating voltage across the junction between the server and the plastic back surface. This radiating voltage could be avoided by may be machining, drilling or milling the conductive fiber filled plastic to allow better low frequency access to the fibers, but this additional manufacturing process is costly.
Referring to a back surface that is entirely or almost entirely metal, a necessary conductivity will be exhibited to conduct and shield against lower frequency electromagnetic energy. This is because the substantially metal composition allows low frequency energy to smoothly transition through the back surface. However, configuring opening structures in a metal surface to include the bosses discussed above is difficult and costly, particularly as compared with the plastic molding. Without the depth of penetration that is achieved by the bosses, the metal surface will not include waveguides that extend beyond the junction between the server and the back surface, rendering it less effective at shielding the server from higher frequency energy. Therefore, a surface including a composition and shape that will economically shield against both high and low frequency electromagnetic energy is desirable.